Milling tools for shoulder milling, such as shank-end milling tools, may advantageously be used for machining of shoulders, grooves and edges. For the machining of pockets and the like, it is preferable to use a milling tool having a ramping cutting edge portion, i.e. a cutting edge portion that is closer to a central axis of the milling tool than a major cutting edge portion used in the machining, and which is formed at an angle with respect to a surface wiping cutting edge portion. For cost-efficiency, it is preferable to use a milling tool which comprises on one hand a tool body, and on the other hand detachable and replaceable milling inserts.
US2006/0013661 discloses a milling insert and a milling tool intended for shoulder milling. The milling insert is indexable and has a positive basic shape. It comprises an upper side comprising a rake surface and a lower side opposite to the upper side. The lower side comprises a planar bottom surface serving as a bottom support surface when the milling insert is mounted in a tool body. A side surface extends between the upper side and the lower side around the periphery of the milling insert. A cutting edge is formed between the side surface and the rake surface. The cutting edge comprises a major cutting edge portion, a corner radius cutting edge portion, a ramping cutting edge portion, and a surface wiping cutting edge portion positioned between the corner radius cutting edge portion and the ramping cutting edge portion. The ramping cutting edge portion and the surface wiping cutting edge portion form an angle with respect to each other.
The milling insert disclosed in US2006/0013661 has a “margin” extending below the corner radius cutting edge portion and along the major cutting edge portion, which is formed at a smaller angle than the side surface below the margin with respect to a plane parallel with the cutting edge. In other words, a clearance angle below said portions of the cutting edge is larger near the lower side of the milling insert than near the upper side. The purpose of this is to facilitate the formation of linear walls on the work piece under certain milling conditions. However, this milling insert is not optimized with regard to ease of production. Moreover, the geometry of the milling insert does not enable adaptation of the cutting edge and the clearance surfaces to different milling conditions. Typically, the primary clearance behind the major cutting edge portion will vary along the major cutting edge portion, thus leading to irregular wear of the cutting edge and a strength of the cutting edge which varies along the major cutting edge portion.